The field of this disclosure relates generally to bridged absorbent structures and methods of manufacturing bridged absorbent structures for use in absorbent articles, such as training pants, diapers, incontinence products, disposable underwear, medical garments, feminine care articles, absorbent swim wear, and the like.
In one general practice of forming fibrous webs, such as laid fibrous webs, a fibrous sheet of cellulosic or other suitable absorbent material is fiberized in a conventional fiberizer, or other suitable shredding or comminuting device, to form discrete fibers. In addition, particles of superabsorbent material are often mixed with the fibers. The fibers and superabsorbent particles are then entrained in an air stream and directed to a suitable foraminous forming surface upon which the fibers and superabsorbent particles are deposited to form a continuous absorbent fibrous web or discrete absorbent structures.
The forming surfaces utilized in such systems are typically constructed with a wire or screen grid and employ a suitable pneumatic flow mechanism, such as vacuum suction apparatus, to define a differential pressure zone on the forming surface and impose a pressure differential thereon. The pressure difference usually results in airflow through the openings or perforations in the screen or grid of the forming surface. The use of vacuum suction to draw the air-entrained fiber stream onto the forming surface, and pass the airflow through the forming surface has been employed in high-speed commercial operations.
Various mechanisms have been used during the formation process to produce gradations in basis weight of the resultant fibrous web. For example, suitable forming surfaces have been constructed with depressions or pocket regions for the formation of desired high-basis-weights in the formed fibrous web. Where the pocket regions have been large and deep, it has been difficult to direct desired amounts of fiber material into the pocket regions. In other devices, blocking components have been positioned underneath the forming surfaces to partially block the airflow through the forming surfaces and, thus, inhibit airlaid fibers from being deposited above the blocked off sections.
Some devices form voids in the fibrous web through the thickness of the fibrous web, which can produce gradations in basis weight along the fibrous web. However, the voids formed in the fibrous web are free from any fibrous material and penetrate through the entire depth of the fibrous web. As a result, the voids can affect the structural integrity of the web and do not allow for additional gradations of basis weight. Further, the known methods for producing gradations in basis weight along the fibrous webs do not provide gradations in the basis weight through the low basis weight areas of the fibrous web.
Accordingly, it is desirable to provide more reliable and more efficient methods and apparatus for forming laid fibrous webs having gradations of basis weight. It is further desirable to provide easily assembled and modified apparatus for forming laid fibrous webs.